1. Field of the Invention
The present invention relates to balloon articles and to methodology for making same, in particular a balloon useful for in vivo lumenal medical procedures, having enhanced robustness, expansibility (inflation) and isotropy characteristics, relative to balloons of the prior art.
2. Description of the Related Art
Various balloon articles are in use for cardiovascular and other medical procedures (such as percutaneous transluminal angioplasty, percutaneous transluminal nephrostomy, ureteral dilatation, biliary duct dilatation, percutaneous transluminal renal angioplasty, and the like).
Examples include so-called high pressure balloons for percutaneous transluminal angioplasty treatment applications, in which the balloon is introduced into an arterial lumen to deform (flatten) a blood clot or plaque on an arterial wall surface, as well as balloons that are otherwise stent-deployed into a cardiovascular locus.
High pressure balloons are generally formed of materials such as PET, nylon, Isoplast(copyright) and other highly rigid and crystalline polymers whose high pressure strength derives from crystallization of the base of the polymer. Such balloons are pressurized to levels on the order of 6-12 atmospheres (90-180 psi).
Such high pressure balloons of the prior art have the problem attributable to their pre-shaped character that when folded for stent deployment, the folded balloon article forms xe2x80x9cwings,xe2x80x9d i.e., flattened protruberant portions of the balloon, that make it difficult to deploy the balloon in vivo from the stent. Further, because of its floppy, xe2x80x9cwingedxe2x80x9d conformation, the folded balloon article is susceptible to disengaging from the stent, thereby rendering it extremely difficult in some instances to properly position the stent.
Other examples of balloon articles used in the art include so-called low pressure balloons, which are inflated to a pressure on the order of 1-3 psi. Low pressure balloons are used in cardiovascular applications for blocking blood flow, or for removing/blocking a blood clot. In such applications, the balloon is typically bonded to the shaft of a catheter, and after inflation and use, the balloon is readily retracted to an original catheter sleeve shape
Low pressure balloons are typically formed of latex. Latex is a superior material for such balloon articles, since it is very soft and flexible in character, has high elongation and good memory characteristics, and exhibits low creep, but latex allergic reaction and susceptibility are increasingly recognized as a major issue confronting the use of latex articles of all types.
Another issue confronting the use of balloon articles for in vivo usage is the asymmetric character of the inflation,
An ideal solution to the above-described winging problem associated with high pressure balloons would be the provision of a semi-compliant balloon that has a low profile or sleeve shape that can expand to a desired size (radius), that is amenable to high pressure inflation and that when deflated contracts to a shaft sleeve or an original low profile shape.
In low pressure balloon applications, an ideal solution to the latex allergic reaction and susceptibility issue would involve the availability of another material that is free of the allergenic issues associated with latex, exhibits low creep and high elasticity, and is readily bondable to a catheter shaft. There are otherwise non-allergenic materials that possess high elasticity character, e.g., silicone, but such materials are not easily bonded to the catheter shaft. Other materials exist that are more readily bondable and have good elasticity characteristics, e.g., polyurethanes, but such materials have unsatisfactory creep characteristics.
The aforementioned ideal solutions do not exist in the current state of the art, which continues to seek improvement in balloon articles for cardiovascular and other applications.
The present invention relates in one aspect to a balloon article comprising a balloon formed of a partially UV-cross-linked polyurethane material.
The invention in another aspect relates to an ultraviolet radiation-crosslinked balloon article formed of a homogeneous composition including a UV-cross-linkable polyurethane material, a cross-linker component that is cross-linkable by free-radical polymerization, and a free-radical source material generating free radicals in exposure to ultraviolet radiation, wherein the homogeneous composition is partially cross-linked by exposure to ultraviolet radiation, and wherein the balloon article is resiliently deformable from and resiliently recoverable to an initial shape of the article.
A still further aspect of the invention relates to a method of fabricating a balloon article for in vivo lumenal use, comprising the steps of: forming a precursor structure for the balloon article of a homogeneous composition including a cross-linkable polyurethane material, a cross-linker component that is cross-linkable by free-radical polymerization, and a free-radical source material generating free radicals in exposure to ultraviolet radiation, and exposing the precursor structure to ultraviolet radiation for sufficient time and under sufficient radiation intensity to partially cross-link the composition, to yield the balloon article.
Other aspects, features and embodiments of the invention will be more fully apparent from the ensuing disclosure and appended claims.